Ios 访问alertController中声明的变量

我正在尝试创建一个提醒，提示用户命名他们导入到音乐表显示应用程序的歌曲

我已为此命名过程创建了一个函数：

- (NSString *)nameImportedSong {
    NSString *songName;

    UIAlertController * alertController = [UIAlertController alertControllerWithTitle: @"New Song"
                                                                              message: @"Choose a song name"
                                                                       preferredStyle:UIAlertControllerStyleAlert];
    [alertController addTextFieldWithConfigurationHandler:^(UITextField *textField) {
        textField.placeholder = @"song name";
        textField.textColor = [UIColor blueColor];
        textField.clearButtonMode = UITextFieldViewModeWhileEditing;
        textField.borderStyle = UITextBorderStyleRoundedRect;
    }];
    [alertController addAction:[UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
        NSArray * textfields = alertController.textFields;
        UITextField * namefield = textfields[0];
        NSString *chosenSongName = [NSString stringWithFormat:@"%@", namefield.text];

    }]];

    songName = ; // <-------------how do I assign chosenSongName to songName?

    [self presentViewController:alertController animated:YES completion:nil];

    return songName;

}

-（NSString*）名称导入歌曲{
NSString*歌曲名；
UIAlertController*alertController=[UIAlertController alertControllerWithTitle:@“新歌”
信息：@“选择歌曲名称”
首选样式：UIAlertControllerStyleAlert]；
[alertController addTextFieldWithConfigurationHandler:^（UITextField*textField）{
textField.placeholder=@“歌曲名称”；
textField.textColor=[UIColor blueColor]；
textField.clearButtonMode=UITextFieldViewMode编辑时；
textField.borderStyle=UITextBorderStyleRoundedRect；
}];
[alertController addAction:[UIAlertAction actionWithTitle:@“确定”样式：UIAlertActionStyleDefault处理程序：^（UIAlertAction*操作）{
NSArray*textfields=alertController.textfields；
UITextField*namefield=textfields[0]；
NSString*chosenSongName=[NSString stringWithFormat:@“%@”，namefield.text]；
}]];
songName=；//对变量使用_块关键字

__block NSString *chosenSongName;

 [alertController addAction:[UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
    NSArray * textfields = alertController.textFields;
    UITextField * namefield = textfields[0];
    chosenSongName = [NSString stringWithFormat:@"%@", namefield.text];

}]];

songName = chosenSongName;
NSLog(@"chosenSongName = %@",chosenSongName);

对变量使用_块关键字

__block NSString *chosenSongName;

 [alertController addAction:[UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
    NSArray * textfields = alertController.textFields;
    UITextField * namefield = textfields[0];
    chosenSongName = [NSString stringWithFormat:@"%@", namefield.text];

}]];

songName = chosenSongName;
NSLog(@"chosenSongName = %@",chosenSongName);

非常好，谢谢，非常好，谢谢。